The present invention relates to a valve, in particular a ball valve, which comprises a base body with a passage opening, a movable valve member for closing and opening the passage opening and an actuating mechanism, by means of which the valve member can be moved in order to open up the passage opening, the actuating mechanism having at least two elements in wire form made from a shape memory alloy, which are secured to the base body or a carrier body connected thereto and can be shortened in the event of the temperature rising to a temperature above a threshold temperature.
Valves play an important role in many technical fields in order to control the flow of a medium. They can also be used to meter defined volumes and to provide or block off continuous streams of fluid. Actively switching valves are moved from the closed state into the open state or vice versa when energy is supplied. In many applications, the actuating mechanism for opening and if appropriate closing the valves needs to take up as little space and energy as possible.
DE 38 35 788 A1 has disclosed a fast-switching ball valve which comprises a base body having a passage opening, a ball for closing and opening the passage opening and an actuating mechanism which can be used to move the ball in order to open up the passage opening. In the closed state of the valve, the ball is pressed onto the passage opening by the applied pressure of the gas flow. To open up the passage opening, the actuating mechanism moves the ball away from the passage opening. For this purpose, an actuating element of the actuating mechanism exerts a lateral impact on the ball, which is then released from the passage opening or the valve seat of the passage opening. The ball is returned to the valve seat under the influence of the gas flow which is introduced. In this document, a pulse-operated electromagnet is used as actuating mechanism for displacement of the ball, and after actuation the electromagnet is returned to the starting position by a spring force. An actuating mechanism with an electromagnet of this type takes up considerable space, however, and also consumes too much energy for many applications.
W. Ehrfeld et. al. “Mikroactoren-Wirkprinzipien, Fertigungstechnologien und Applikationen” [Micro-actuators-principles of operation, manufacturing technology and applications] in Rainer Nordmann et al. (Eds.): Kolloquium Aktoren in Mechatronischen Systemen Mar. 11, 1999, pages 14–16 has described a fast-switching micro-ball valve with a ball size of approx. 100 μm, which is actuated by a piezo-ceramic multilayer actuator. The advantage of this valve is the small overall size and the low energy consumption for the piezo-ceramic actuator used as drive compared to an electromagnetic drive. However, one drawback of this piezo-ceramic actuator is that it can only generate displacements in the μm range. Consequently, this actuating mechanism is not suitable for actuating the ball of a larger ball valve.
In this configuration too, the ball is only knocked off the valve seat for a short time and in pulsed fashion before then returning to its original position as a result of the flow of liquid. If the open valve state is to be maintained for a longer period of time, in both the above-mentioned valves a rapid succession of repeated actuations of the actuator is required. This constantly consumes energy for as long as the valve is to remain open.
Documents DE 199 61 736 A1, DE 39 35 474 A1, DE 37 44 240 A1 and DE 36 08 550 A1 describe valves which have piezo-electric actuators for actuating the valve bodies. For example, DE 199 61 736 A1 presents a valve which has a sealing element which is held on a piezo-electric bending transducer and can be used to close off a valve passage.
DE 100 62 704 A1 describes an electromechanical component having at least two actuators made from a shape memory alloy, which change shape when a defined temperature is reached and move as a result of this change. One significant feature of the component described is that the two actuators in each case change shape at different temperatures.
Documents DE 697 09 529 T2, DE 199 63 499 A1, DE 43 22 731 A1, DE 36 35 216 A1, U.S. Pat. No. 5,345,963 A, U.S. Pat. No. 4,973,024 A and JP 61103081 A describe valves in accordance with the preamble of patent claim 1, in which the elements in wire form, which consist of a shape memory alloy, constantly have to be moved against a further stressing element, preferably a spring, during closing or opening of a valve. The movement of the valve member in at least one direction, i.e. either opening or closing of the valve, is in this case effected with the aid of an additional spring element.
The object of the present invention is to provide a valve, in particular a ball valve, having a compact and energy-efficient actuating mechanism which can be used even for actuating displacements in the millimeter range.